Abstract: In order to compare the effects of different water treatments on soil respiration,root stock biomass and net root biomass of Stipa breviflora desert steppe under different grazing intensities,and study the relationship between soil respiration and underground biomass,we conducted comparative experiments in different grazing intensity experimental areas of Stipa breviflora desert steppe in Inner Mongolia. The 50 hm² experimental plot included four treatments with three replicates using a completely randomized block design,and four treatments were control,light grazing,moderate grazing and heavy grazing respectively. Each grazing treatment included four different water control treatments (50% water reduced,natural rainfall,50% water increased and 100% water increased). In each water control treatment plot,soil respiration was measured by the open-circuit soil carbon flux measurement system LI-8100,and soil cores were collected to measure root stock biomass and net root biomass. The results showed that different grazing intensities had no significant effect on soil respiration and community underground biomass (P>0.05);the soil respiration rate increased significantly with the water addition (P<0.05);the soil respiration showed a increased trend firstly,and then decreased;the root stock biomass in the treatment of 50% reduced water significantly decreased (P<0.05),and the net root biomass in the water addition treatment increased significantly (P<0.05);There was a significant positive correlation between soil respiration and root stock biomass and net root biomass (P<0.05). It indicated that water was the main factor affecting soil respiration and community growth and development in arid desert steppe.

Key words: Grazing, Water, Soil respiration, Underground biomass, Net root biomass

摘要： 为比较短花针茅（Stipa breviflora）荒漠草原不同放牧强度下不同水分处理对土壤呼吸、根系现存量和根系净生长量的影响，揭示土壤呼吸与地下生物量之间的关系，本研究在内蒙古荒漠草原不同放牧强度试验区进行对比性试验。放牧强度试验采用完全随机区组设计，将50 hm²试验样地分为不放牧、轻度放牧、中度放牧和重度放牧4个梯度，3次重复。每个放牧强度下设有4个不同水分处理（减水50%、自然降水、增水50%和增水100%）。在不同水分处理小区内，采用开路式土壤碳通量测量系统LI-8100测定土壤呼吸速率，用根钻法测定根系现存量，根袋法测定根系净生长量。结果表明：不同放牧强度对土壤呼吸和群落地下生物量没有产生显著性影响（P>0.05）；土壤呼吸速率随着降水的增多显著增加（P<0.05）；在整个生长季中，土壤呼吸速率呈现先增高后下降的趋势；群落地下生物量在减水50%处理下显著降低（P<0.05），根系净生长量在增水100%处理下最高，显著高于减水50%处理（P<0.05）；土壤呼吸速率与根系现存量和根系净生长量存在显著的正相关关系（P<0.05）。因此，在干旱的荒漠草原，水分是影响土壤呼吸和群落生长发育的主要因素。

关键词: 放牧, 水分, 土壤呼吸, 地下生物量, 根系净生长量